SSR Monitoring in EMS

Bill BlevinsManager, Operations Planning

04/21/232

Agenda

Purpose

SSR Displays

Discussion

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Stations with Series Capacitors Actual and Planned

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SSR concerns

For the modes in which the generator participates, the generator’s rotational speed will oscillate around the normal operating speed. If fm is the frequency of the oscillatory component of the machine speed and if f0 is the system frequency associated with the normal operating speed, then the generator oscillation will result in electrical currents being injected into the system at complementary sideband frequencies of f0, specifically f0-fm and f0+fm. These currents result in a pulsating torque on the generator rotor that is passed into the turbine-generator mechanical system through the shaft connecting the different masses of the mechanical system. If the frequency of this torque is near one of the torsional mode frequencies, the group of masses participating in the mode will oscillate against each other across the shaft connecting the masses. This causes additional stresses in the shaft.

A “worst case” for series capacitor SSR is depicted by the IEEE First Benchmark System shown in Figure 2.1-4. This is a highly compensated radial transmission system that exhibits classical SSR characteristics. The IEEE First Benchmark System is based on the Navajo plant (a plant with quite complex SSR potential) and comprises a single 892.4 MVA dynamic machine model connected to an infinite bus via a 75% series compensated 500 kV transmission line. In this Benchmark System both positive sequence (R1, X1) and zero sequence (R0, X0) system impedances are specified when appropriate. The level of series compensation in the line was chosen to cause undamped torsional oscillations on the generator shaft in the absence of any mitigating measures as shown

04/21/235

EMS SSR Alarm System Features 

SSR risk increases when certain combinations of

specific lines or transformers are out of service.

The system detects complex outage conditions that

may place a generator at elevated risk for sub-

synchronous resonance (SSR).

Subsynchronous Resonance (SSR) Alarms developed

to aid in real-time and study applications when the

series capacitors should be bypassed.  

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EMS SSR Alarm System Features

  This project provides

SSR Alarm displays for the use of current business

users (System Operators/Shift Engineers).

Alarm system similar to the RAS editor where SSR

Alarms setup in an application similar to the RAS.

Display details of SSR’s to the control room.

Archive SSR Alarms messages info which is saved

and replicated to the data warehouse.

SSR generated Alarms available for real time and

study.

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SSR DISPLAYSSSR DISPLAYS

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Network Online Sequence Display

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Contingency Violation Display

04/21/2310

TCM Display

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SSR Summary Display

EXAMPLE ONLY

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SSR Trigger Details Display

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SSR Summary Display

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RAS Editor

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RAS Editor

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SSR Summary Display

04/21/2317

Business Process For SSR

 

Develop Criteria for NPRR

Develop Criteria for Operations Departments

Monitoring.

Training the Operators / Engineers(April 15th)

New Departmental Procedures(TBD)

Update Control Room Operating Procedures(TBD)

Possible GTL to create for handling when Series

Capacitors need to be bypassed.

04/21/2318

Discussion/Questions? Discussion/Questions?